The present invention relates to a method of manufacturing electronic components for use in electronic equipment. More particularly, the present invention is a method of manufacturing electronic components using intaglio printing.
The recent trend towards the downsizing of electronic equipment has created a corresponding need for the downsizing of electronic components. Under these circumstances, it is desired in the conductor patterns of electronic components that conductors constituting the patterns should be finer and conductive films should be thicker for reduction of conductor resistance. Further size reduction requires multi-lamination of circuit boards.
To meet these requirements, for example, Japanese Patent Laid-Open Publication No. H07-169635, discloses an intaglio printing method using an intaglio made of a flexible film and having a fine wiring pattern groove processed thereon.
In an ordinary intaglio printing method, conductive paste is left inside of the intaglio and the remaining paste often causing printing failures. Therefore, in the method disclosed above, a releasing layer made of a fluorocarbon releasing agent is formed over the surface of the intaglio so that the conductive paste, the substance to be transferred, can be transferred onto a substrate efficiently. This layer allows the conductive paste filled in the intaglio to be easily removed therefrom, thereby reducing printing failures.
The materials and method of forming the above-mentioned releasing layer are disclosed in Japanese Patent Laid-Open Publication No. H04-246594 and Japanese Patent Laid-Open Publication No. H04-332694. That is, as illustrated in FIG. 5, to dip intaglio 21 into solution 22 containing releasing agent dissolved therein to form a releasing layer on the surface of the intaglio. The intaglio is treated in vessel 30 using a fluorocarbon silane releasing agent. Sometimes during the treatment, bubbles 40 may be entrapped in recesses of the intaglio.
The above-mentioned intaglio printing method, however, has a problem with durability of the releasing layer in that the releasing layer on the surface of the intaglio comes off every time it is used for printing and thus the releasing ability deteriorates. As patterns to be printed become finer, finer grooves must be processed on the intaglio. Therefore, in the method of forming a releasing layer on the surface of an intaglio by dipping, the intaglio may be dipped with bubbles entrapped inside of its grooves. In this case, only dipping it even for a long time will not help removing the bubbles entrapped inside of the grooves. For such a reason, the method has a problem in that the bubbles prohibit the contact between the inner walls of the grooves and the releasing agent, so that uniform releasing layer cannot be formed over the whole intaglio. Consequently, the conductive paste is not efficiently transferred from the intaglio onto the substrate and thus such failures as breakage or deformation of wiring patterns are likely to occur.
The present invention is to address the above-mentioned problems. It is, therefore, the object of the prevent invention to realize releasing ability of an intaglio that will not deteriorate even after the intaglio is repeatedly used for printing, and to form a uniform releasing layer over the surface of the intaglio, particularly the inner walls of its micro-processed grooves.
According to the present invention, to accomplish the above-mentioned object, a dual releasing layer is formed on the surface of an intaglio. A first releasing layer directly formed on the intaglio is chemically adsorbed on the substrate of the intaglio; and a second releasing layer formed on the first releasing layer is physically adsorbed on the first layer. In addition, according to the present invention, ultrasonic vibration is applied when the releasing layers are formed over the intaglio.
This method can prevent printing failures previously caused by deterioration of the releasing layer after repeated use of the same intaglio. That is, since the second layer is physically adsorbed on the first layer, the conductive paste peels off from the intaglio at the interface between the second layer and the conductive paste or at the interface between the first and second layers at printing. This ensures printing of the conductive paste onto the substrate. The second layer also serves as a protective layer of the first layer, thus protecting the first layer from deterioration every time the intaglio is used for printing. Furthermore, only adsorbed on the first layer, the second layer can be added prior to printing as required. When the first layer is unevenly formed, the second layer complements the first layer, so that releasing ability of the intaglio is kept constant. In contrast, when the second layer is unevenly formed, releasing ability of the intaglio can be kept constant because the first layer is formed. In addition, when the intaglio is dipped into a solution containing a releasing agent for forming a releasing layer on the surface of the intaglio, ultrasonic vibration is applied. The ultrasonic vibration can remove the bubbles entrapped in the grooves of the intaglio, thus ensuring the reaction of the releasing agent with the intaglio and allowing formation of a uniform releasing layer on the surface of the intaglio.